I am an IH newby looking for some guidance. Thanks in advance. I acquired a 78 Scout with the 304, 4x4, automatic with 67K last fall. Everything looks stock except possibly the carb. It has a Holley (443250-C91 / List 1710-6 / 0945). It ran when I purchased it but had been sitting for 3 years and I think had a blown head gasket and very leaky valve covers. I drained the tank and ran fresh fuel through the system to the carb. When running, it would only run with choke on and would accelerate if you pushed the throttle hard, but engine would act fuel-starved/die if you held the throttle halfway. With choke off, I could get it to a high idle but if you tried to accelerate it would die again. The accelerator pump seemed to work fine when looking down the carb. Fuel pump was working. I could find no obvious leaks in the manifold after searching everywhere. Next I rebuilt the carb with OEM parts kit. No change, engine acts exactly the same as before. I readjusted the float level to spec. No change. Also played with mixture screw and advanced/retarded timing. Again, no change at any setting.

Since then, I tested compression (155-160 on all cylinders).

I then changed head gaskets, valley pan gaskets, valve cover gaskets, valve gaskets, intake and exhaust manifold gaskets, and cleaned and repainted the whole top end of the engine. Heads, valves, cylinders all looked clean. Also changed the points and condenser which were working fine but were pretty old and put in new plugs. Also changed the leaky oil pan gasket and thermostat. I discarded the old AC compressor.

Engine started right up and sounds 100% better, but has the same issue as before. It will run great at high RPM at idle with the choke on but wont or barely idle with the choke off. It will accelerate somewhat smoothly with the choke on, but with the choke off it cuts out when you try to give it gas.

So, am I not letting it warm up enough? I have not ran it for more than 10 minutes because of this issue. Is it the carb? Any ideas? Thank you!

That list number carb denotes it as a Holley model 2300 original design. It is not original to your vehicle, as you suspected. It would have been original to an earlier model International vehicle. Those are generally good carbs when they aren't too worn out, or haven't been monkey-fudged by previous owners or when they haven't been subjected to mass production, assembly line mentality re-manufacuring processes. The symptoms you've described indicate a fuel delivery issue within the carb itself. There appears to be an overly lean condition at part throttle. There are a number of potential causes. There could be mismatched parts in play. There could be worn out parts in play. Without knowing the history and overall condition of the carb, its a crapshoot. I don't know how married you are to that carb, nor how much of a science project you're willing to take on versus your available budget. In this case, you could well be much time and frustration ahead to ditch that carb in favor of a brand new, aftermarket Holley 2300 in 350 cfm delivery. The list 0-80350 and list 0-7448 are popular choices.

Hey thank you for the guidance. That was going to be my next move, just swap it out for a new 2300 0-7448 or a Motorcraft 2100 300cfm. Do you think its worth sending the carb I have to a reputable rebuilder who knows what they are doing? It appears to be in great shape.

If you know of one. Not someone who's going to media blast it and slap it back together with whatever parts might be handy. The cause of your issues can run from simple to complex. It might just be a mismatched gasket, or the wrong size jets. Either of which would be simple to remedy by someone who was capable of recognizing the problem.